A question which contains something like "How can I do ABC
without using XYZ
" always makes me wonder why such apparently arbitrary restrictions are imposed?
What is wrong with using a module? The very existence of CPAN with its unique wealth of modules extending the power of Perl is something which makes all other programming languages envious, so why should you not take advantage of it?
A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James